Relative to turbomachine components composed of superalloy materials, turbomachine components composed of advanced ceramics are capable of achieving increased temperature tolerances, lower densities, and weight savings for flight applications. Ceramic turbomachine components are not without limitations, however, and are often prone to deleterious chemical reactions within the high temperature turbomachine environment. Turbomachine components composed of silicon-ceramic materials, for example, are susceptible to recession due to high temperature reactions with mixtures of water vapor and oxygen (colloquially, “steam”). The silicon contained in such silicon-ceramic materials readily oxides to form silica, which may then react with steam at elevated temperatures to form volatile silicon hydroxide. Sublimation of the silicon hydroxide accelerates erosion of the silicon-ceramic material and drives recession of the component body. EBCs can be formed over the gas-exposed surfaces of ceramic turbomachine components for enhanced protection from high temperature reactions. This is an imperfect solution, however. Conventional EBCs rely on metallic bondcoats to join the EBC to the underlying component body. The EBCs may be prone to ingress of high temperature steam, which may penetrate to the underlying metallic bondcoat. The metallic bondcoat may itself contain silicon and, thus, may be similarly prone to structural degradation due to detrimental high temperature reactions; e.g., such reactions may result in bondcoat expansion, oxidation, and fractures leading to premature EBC spallation and failure.
An ongoing demand thus exists for methods by which protective coatings and coating systems can be formed over ceramic turbomachine components and other high temperature ceramic components, while overcoming the limitations identified above. Ideally, embodiments of such methods would permit the formation of high temperature coating materials over ceramic components in a manner reducing, if not eliminating reliance upon silicon-containing metallic bondcoats, whether such coating materials ultimately serve as a standalone protection solution, as a non-metallic bondcoat over which additional coating layers are formed, or as a precursor material further modified by additional processing to yield the final high temperature coating or coating system. It would also be desirable for methods to enable components having relatively complex surface geometries to be coated in a thorough and controlled manner. Other desirable features and characteristics of embodiments of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying drawings and the foregoing Background.